This invention relates to rectifier assemblies, and more particularly, this invention relates to rectifier assemblies used with engine-driven alternating current generators and methods of constructing same.
Engine-driven alternating current generators require rectifier assemblies for rectifying alternating current into a direct current suitable for use with automotive electronic components. Typically, automotive rectifier assemblies use heat sink plates that include press fit diodes.
Examples of rectifier assemblies as described include those rectifier assemblies disclosed in commonly assigned U.S. Pat. No. 5,451,823, issued Sep. 19, 1995, and U.S. Pat. No. 5,991,184, issued Nov. 23, 1999, the disclosures which are hereby incorporated by reference in their entirety.
Some of the prior art rectifiers, however, do not have adequate diode electrode clearance, efficient diode positioning, and adequate ventilation for cooling the diodes.
U.S. Pat. No. 4,952,829, Armbruster et. al. discloses a single insulator, conductor embedded integument that is positioned between two heat sinks formed as electrically conductive plates that can correspond to negative and positive heat sinks that receive respective negative and positive diodes. The integument encloses embedded conductor leads for interconnecting the diodes, stator leads, and other components used in these rectifier assemblies. This type of integument typically includes a single circuit board. The single integument interconnects seventeen diodes and six stator leads of an alternator stator, corresponding typically to the non-rotating part of the structure. The complexity of these single integuments with embedded conductors sometimes requires the formation of multilayer conductors that are electrowelded to form a desired circuit configuration. If an electroweld is weak or improperly fabricated, it is not possible to perform a visual inspection after the conductors are embedded.
This relatively large, single integument also restricts the air flow between the outer and inner conductive plates. Because rectifier diodes are located near the end of these plates, the diodes are not sufficiently cooled and are prone to failure. Furthermore, each different alternator application requires an expensive mold to manufacture a single circuit board for the integument, resulting in a large inventory of parts. Furthermore, as new alternator applications develop, a single integument as described requires extensive design and tooling changes, even with simple design changes. Also, a single conductor embedded integument restricts equalized heat dissipation because it is not symmetrically formed.
In U.S. Pat. No. 5,331,231, Koplin et. al., a threaded bolt is used as an output terminal and positioned between two rectifier plates. This bolt is mounted from the inner side of an outer rectifier plate and held in position by a common, threaded nut on the outer side of the rectifier plate. The threaded bolt is placed between two conductor plates, which receive press fitted rectifier diodes. These plates are electrowelded to opposite sides of the single integument, making the removal and replacement of the threaded bolt impractical. No particular advantage has been gained by securing the bolt with a common nut, which is also subject to loosening by vibration. The additional production step required for assembly of this rectifier is not advantageous.
In accordance with the present invention, a rectifier assembly and method of forming same is disclosed, which can be used on a variety of applications of various output current capacities and external connectors by using a small number of universal and specially designed components that minimize tooling costs and reduces the inventory of single application components, which may have a questionable usage rate. The present invention also improves the performance of single application type components by increasing the speed of assembly, and allowing a robust and sturdy rectifier assembly construction that can withstand severe vibration and extreme temperature variations, and have an extended thermal cycling life and corrosion protection. Each rectifier assembly can be used specifically for an intended application.
The rectifier assembly of the present invention includes opposing, substantially identical heat sink plates that are interchangeable as either positive or negative heat sinks. Three identical standoffs with snap in wedges are located at key mounting areas Three identical stator guides xe2x80x9csnap inxe2x80x9d for an interconnection between the stator lead and diode anode leads. Three identical center tap guides that xe2x80x9csnap inxe2x80x9d use the tabs. It is possible to electroweld a preformed semicircular conductor ring and other preformed conductors if center tapped diode connections are required. A trio diode mount connects smaller preformed diodes to stator leads. A stud, spade, threaded, or side connector allows external interconnects in any combination for a required specific application.
The rectifier assembly of the present invention includes two substantially identical and interchangeable heat sink plates mounted parallel to each other in spaced relation. Each heat sink plate has identically positioned diode mounting holes. A plurality of rectifier diodes are mounted within the diode mounting holes. Each diode has a diode electrode. One plate is selectively negative or positive depending on the polarity of diodes mounted within the plate such that one heat sink plate is negative and the other heat sink plate is positive. The diode mounting holes not receiving diodes therein provide diode electrode clearance and ventilation. Standoffs can be formed of an insulator material and mounted between the two heat sink plates for separating the two plates and can be mounted by snap fit connection. Component attachment positions are formed on the heat sink plates for receiving a stator lead guide, center tap guide, threaded output terminal, trio diode mount for field excitation diodes, standoffs, side connectors, stud terminal, or spade terminal.